In response, the Labour candidate's team suggested the Tory's choice of words could be seen as a "coded racist attack."

Speaking to the BBC, Mr Goldsmith said changes in the Labour Party in the last few months had been "extraordinarily radical".

Dan Kitwood

Zac Goldsmith accused Sadiq Khan of playing the race card

He added: "I think he is playing with fire. I don't think there is anything more divisive than playing the race card when clearly, unambiguously, it does not apply.

"It 's very obvious that what I was referring to when I described him as a radical candidate as part of a radical process that has enveloped the Labour Party and taken our politics in an extraordinary direction."

A spokesperson for Mr Khan's campaign said: "It was the Zac Goldsmith campaign which put out the infamous dog-whistle leaflet branding Sadiq as "radical" just because he happens to be a Muslim.

Reuters

In response, Sadiq Khan's team accused Goldsmith of dog-whistle politics

"And it was Zac Goldsmith's campaign which had to launch an investigation after alleged racist remarks from a Tory canvasser to a voter.

"Their campaign is already so desperate that they've resorted to [Tory election guru]Lynton Crosby's divisive dog-whistling because they simply have no answers to the challenges London faces like fixing the housing crisis and keeping fares down."

It's the latest in a string of bitter rows between the two main candidates in May's election.

Yesterday, Mr Khan accused Mr Goldsmith of never having had a "proper job".

Challenged to say whether he would be " Jeremy Corbyn 's man in London" if he takes office at City Hall, Mr Khan told the BBC: "I think I am my own man."

And he added: "Jeremy Corbyn isn't on the ballot paper in the May mayoral elections. Nor is David Cameron .

Nigel French/PA Wire

Mr Khan maintains he is not "Jeremy Corbyn's man"

"I am. So I have got to set out over the course of the next 120 days who I am."

The Tooting MP said the windfall tax was one of a number of examples of areas where "it is important for me to be my own person".

But he added: "What I am not going to do is for the next three months differentiate myself from Jeremy Corbyn , because I will speak for my own policies and my own vision for this great city, and let Jeremy do the important job of being leader of the Labour Party."

He declined to comment on speculation of an upcoming reshuffle in the shadow cabinet.

" Jeremy Corbyn is the leader of the party. That is a decision for Jeremy to take. My job is to tell Londoners why they should lend me their votes to make London an even greater city than it already is."